1. Technical Field
The present invention generally relates to a process for preparing a para-branched mono-alkyl-substituted hydroxyaromatic compound.
2. Description of the Related Art
Long chain para-alkylphenols lead to high-performance surfactants that are widely used in the manufacturing of lubricating oil additives. It is well known to prepare alklylphenols by alkylating phenol with branched olefins over ionic exchange resin catalysts.
Branched para-alkylphenates are a key component for making detergents for use in marine lubricants. One manufacturing process for preparing branched para-alkylphenates involves alkylating regioselectively an excess of phenol with a branched olefin in presence of an ionic exchange resin catalyst. Under the conditions used, the acidic resin heavily favors the formation of the desired para-alkylphenol isomers (95%) at the expense of the ortho-isomer (5%), which has a tendency to drastically decrease the surfactant performance. Subsequent steps of basification of branched para-alkylphenates followed by vulcanization and overbasing treatment of the resulting calcium alkylphenate (CAP) complete the sequence.
The resulting CAP detergent can contain a substantial amount of the residual monalkylphenol as an ortho alkylphenol isomer (e.g., tetrapropenylphenol (“TPP”)). The presence of the bulky aliphatic chain in close proximity to the hydroxyl group may prevent the ortho-alkylphenol to react further, and consequently remain as is in the final product. One potential approach to decrease the amount of this residue is to increase the already high para selectivity (95%) of the phenol alkylation to prepare TPP. By improving the regioselectivity of the alkylation of phenol in favor of the para isomer, less residual TPP may remain in the finished product.
U.S. Pat. No. 3,953,538 discloses an alkylation process in which a stream of an olefinic material is mixed with an acid stream and polymerized to cause formation of a polymeric diluent for the high strength acid which is initially charged to the alkylation process.
U.S. Pat. No. 4,225,737 (“the '737 patent”) discloses a process for the alkylation of an aromatic hydrocarbon with an olefin-acting alkylating agent. The process disclosed in the '737 patent involves (a) commingling an aromatic hydrocarbon and a first portion of the olefin-acting alkylating agent at alkylation reaction conditions in a first alkylation reaction zone in contact with a hydrofluoric acid catalyst; (b) separating the effluent from the first alkylation reaction zone into an acid phase and a hydrocarbon phase comprising alkylate and unreacted aromatic hydrocarbon; (c) commingling the hydrocarbon phase with a second portion of the olefin-acting alkylating agent at alkylation reaction conditions in a second alkylation reaction zone in contact with the acid phase transferred from the first to said second reaction zone by maintaining a pressure differential between the first and second zones of from about 5 to about 20 psig.; (d) separating the effluent from the second alkylation reaction zone into an acid phase and a hydrocarbon phase and recycling the former to the first alkylation reaction zone; and, (e) recovering an aromatic alkylation product from the last-mentioned hydrocarbon phase.
U.S. Pat. No. 4,536,301 (“the '301 patent”) discloses a surfactant slug used to recover residual oil in subterranean reservoirs. The slug disclosed in the '301 patent comprises a mixture of (1) from about 1 to about 10% of a sulfonate of a mixture of mono- and dialkyl-substituted aromatic hydrocarbon which has been obtained by the alkylation of an aromatic hydrocarbon with an olefinic hydrocarbon in the presence of a hydrogen fluoride catalyst; (2) a lower alkyl alcohol which possesses from about 3 to about 6 carbon atoms; and (3) a nonionic cosurfactant comprising an ethoxylated n-alcohol which possesses from about 12 to about 15 carbon atoms.
U.S. Pat. No. 4,816,185 discloses reaction products of C9-C30 alkylbenzenes with styrene and sulfonated derivatives thereof and processes for preparing such products and derivatives. The sulfonate salts of reaction products are especially useful as detergents.
U.S. Pat. No. 5,750,818 discloses a process for the liquid phase alkylation in an alkylation reactor of a hydrocarbon substrate with an olefinic alkylating agent in the presence of an acid alkylation catalyst at least one hydrocarbon having a lower boiling point than the hydrocarbon substrate and with a substantial stoichiometric excess of the hydrocarbon substrate over the alkylating agent to form a liquid product mixture.
U.S. Pat. No. 6,054,419 discloses a mixture of alkyl aryl sulfonates of superalkalinized alkaline earth metals comprising (a) 50 to 85% by weight of a mono alkyl phenyl sulfonate with a C14 to C40 linear chain wherein the molar proportion of phenyl sulfonate substituent in position 1 or position 2 is between 0 and 13% and (b0 15 to 50% by weight of a heavy alkyl aryl sulfonate, wherein the aryl radical is phenyl or not, and the alkyl chains are either two linear alkyl chains with a total number of carbon atoms of 16 to 40, or one or a plurality of branched alkyl chains with on average a total number of carbon atoms of 15 to 48.
U.S. Pat. No. 6,551,967 discloses a low overbased alkaline earth metal alkylaryl sulfonate having a Total Base Number of from about 2 to about 30, a dialkylate content of 0% to about 25% and a monoalkylate content of about 75% to about 90% or more, wherein the alkylaryl moiety is alkyltoluene or alkylbenzene in which the alkyl group is a C15-C21 branched chain alkyl group derived from a propylene oligomer are useful as lubricating oil additives.
U.S. Pat. No. 6,989,355 discloses an under-neutralized alkylxylene sulfonic acid composition for enhanced oil recovery processes. The patent also discloses a method for enhancing the recovery of oil from a subterranean reservoir which method employs the under-neutralized alkylxylene sulfonic acid compositions. The under-neutralized alkylxylene sulfonic acid compositions are employed in an aqueous media. The method optionally employs suitable co-surfactants, such as alcohols, alcohol ethers, polyalkylene glycols, poly(oxyalkylene)glycols and/or poly(oxyalkylene)glycol ethers.
It is desirable to provide an improved process for preparing a para-branched mono-alkyl-substituted hydroxyaromatic compound.